Magnetic latch



June 1961 v. K. FREMSTAD 2,990,210

MAGNETIC LATCH Filed June 11, 1956 REA/57,90

1 INVENTOR.

ates

This invention relates to a latch for securing members such as swinging doors of cabinets, cupboards, closets, or other objects, wherein the latching action between the door and the door jamb, or other member, is produced by the magnetic attraction of a magnet in the latch to an armature or strike plate.

This is a continuationin-part of my applications Serial Nos. 516,629 and 516,661; both filed on June 20, .1955, now abandoned.

Latches of this type possess advantages over mechanical latches in that they are quiet in their action. They avoid rattling or chatter in latched objects by positively retaining the latched members in engaged relationship without leaving any free space between the latching members for vibration to occur.

To compete with mechanical latches, the magnetic latch should be constructed of parts that are capable of being mass-produced by methods involving relatively few operations. The parts of the latch should be designed for rapid assembly, and the assembled latch should be adapted for rapid and convenient installations in the cabinet, or other object, with simple tools.

Of particular importance in magnetic latches, is the manner of mounting the magnet in its housing. The mounting should be such that the magnet is loosely mounted and relatively balanced for ready adjustment of its position with respect to the armature. When thus mounted, the magnet can compensate for any small deviations from perfect alignment of the latching members.

Accordingly, an important object of my invention is to provide a magnetic latch of the type described above wherein the magnet is mounted in its housing for rapid and accurate adjustment of its position relative to the armature, or strike plate, so that a maximum of magnetic attraction can be brought into action between the latching members.

Another object is to provide such a magnetic latch consisting of a minimum number of parts and made of efficient design and construction for economic massproduction and rapid assembly.

A further object is to provide such a magnetic latch that is designed for rapid and convenient installation with simple tools.

Additional objects will become apparent from the following descriptions:

Stated in general terms, my invention comprehends the provision of a magnetic latch comprising a magnet, pole pieces attracted to the magnet, a pivot means for pivotal movement of the magnet and attracted pole pieces, a non-magnetic housing for the magnet and pole pieces, and an armature, or strike plate for attraction by the magnet. The magnet and the pole pieces preferably are of generally flat shape with the magnet sandwiched between the pole pieces. The outer surfaces of the pole pieces should be smooth so that they will slide readily inside the housing. The inside walls of the housing should be smooth. The housing is constructed so that portions of the pole pieces project therefrom. The pivot means is constructed and positioned so that the magnet and pole pieces can pivot in at least two planes at right angles to each other and so that the strike plate can be attracted with maximum force to the pole pieces and magnet. The projecting portions of the pole pieces are atent ICC adapted to engage a fiat portion of the strike plate, which may be of any convenient design. The magnet and pole pieces are retained loosely and slidably in the housing by detent means, preferably projections extending from the housing across the projecting portions of the pole pieces and the pivot means. The extending portions of the pole pieces may be provided with notches to loosely accommodate the projections. The notches, pivot means and projections preferably are designed and positioned so that the magnet and pole pieces are relatively balanced for ease of movement around the pivot means in the housing during adjustment of their position with respect to that of the strike plate.

A more detailed description of a specific embodiment of my invention is given with reference to the drawing, wherein:

FIGURE 1 is a perspective View showing a specific embodiment of the invention mounted in anelevated kitchen cabinet or wall cabinet;

FIGURE 2 is a vertical sectional view showing the latch and strike plate of FIGURE 1 engaged in latched relationship;

FIGURE 3 is a cross-sectional view, taken as on a line 3-3 of FIGURE 2, showing pivotal displacement of the pole pieces in a horizontal plane;

FIGURE 4 is a view similar to that of FIGURE 2, but somewhat enlarged, and showing the pole pieces in engagement with the strike plate on a warped or misaligned door; and

FIGURE 5 is a front elevational view, taken on the line 5--5 of FIGURE 2, showing the magnet, pivot means and attracted pole pieces disposed in the housing.

In the embodiment shown in the drawing, the permanent magnet 10 is cut to a fiat shape with plane parallel upper and lower sides. A fiat pole piece 1 1 of magnetic material, such as steel, is attracted to one side of the magnet 10, and a second flat pole piece 12 of similar material is attracted to the opposite side of the magnet. The magnet 10 is thus sandwiched between the pole pieces 11 and 12.

The sides of the pole pieces 11 and 12 are parallel planes and preferably are finished to smooth surface. The pole pieces 11 and 12 are cut to about the same length as that of the magnet 10. Both ends of the pole pieces, and of magnet 10, preferably are slightly beveled several degrees from the perpendicular, as best shown in FIGURE 3. The pole pieces are cut to substantially greater width than the magnet, as best shown in FIG- URES 2, 3 and 4, so that side edge portions 13 and 14, respectively, project a substantial, equal distance beyond the side of the magnet 10 when the opposed sides of the magnet and pole pieces coincide.

Notches 16 and 17 are cut into the middle portions of the side edge portions 13 and 14, respectively, to approximately the edge of magnet 10. The notches 16 and 17 are made of somewhat greater width than projections or fingers, 18 and 19 formed on the sides of housing 2.1. The fingers 18 and 19 extend into the notches 16 and 17, over the edges of pole pieces 11 and 12 and partway, at least, over the pivot plate 20 mounted on the edge of magnet 10. The fingers 18 and 19 serve to loosely pivot plate 20, magnet 10 and attracted pole pieces 11 and 12 in the housing 21.

The pivot plate 20 preferably is made of non-ferrous material, such as Phosphor bronze, for example. It is provided with an outer surface preferably curving convexly, that is, in both the horizontal and vertical directions, as best shown in FIGURES 2, 3 and 4. The convex curvatures of this surface facilitates pivotal movement of the magnet 10 and attracted pole pieces 11 and 12 in the housing around the fingers 18 and 19 in at least both the horizontal and vertical planes.

This permits the protruding side edge portions 13 and 14 of the pole pieces 11 and 12, respectively, to extend unevenly, as shown in FIGURES 3 and 4, to correct for corresponding unevennesses due to warpage or misalignment of the cabinet door 22, or misalignment of the latch. The protruding edges 13 and 14 of the pole pieces can make the maximum possible degree of contact with the exposed surface of the strike plate 23 by pivoting adequately. in both the horizontal and vertical planes.

-By insuring maximum contact in this manner, maximum forces of attraction are also insured between the pole pieces 11 and 1'2 and the strike plate 23 both when the cabinet door 22 is closed and when it is opened. When the door is closed, the pole pieces move out of the housing 21 to completely contact and strongly and securely hold the door in closed relationship. Likewise, when the door is opened, the pole pieces pivot around pivot plate 20 and attract the door strongly and securely with maximum force until a sharp, sudden break is made between the strike plate and the edges 13 and 14 of the pole pieces.

The pivot plate 20 is provided with an upper projection or car 24 and a lower projection or ear 25. These ears are dimensioned to extend upward and downward, respectively, into notches 16 and 17 of the pole pieces 11 and 12 when the pivot plate is mounted on the magnet and pole pieces, as best shown in FIGURE 5. The ears prevent the pivot plate from turning or sliding sidewise, and the fingers 18 and 19 hold the plate in position against movement outward of the magnet and housing.

The housing 21 is made of nonmagnetic material, such as aluminum, brass or plastics materials, for example, in the form of a case having smooth-surfaced inside walls and With an open side 26. The case preferably is made from a strip of sheet metal. This can be done by shaping the strip of metal, previously cut to a desired pattern, to form ears 27 and 28, provided with elongate screw holes 29 and 30, respectively, and to form a case top 31, bottom 32, ends 33 and 34 and side 35. Bracket portions 36 and 37 are precut in the ends 33 and 34, respectively, and are bent into alignment with the plane of top 31, as shown in FIGURE 5.

Fingers 18 and 19, similarly, are precut in the sides of the top 31 and bottom 32, respectively. The magnet and attracted pole pieces 11 and 12, are disposed in housing case 21 with side edge portions 13 and 14 of the pole pieces protruding from the open side 26 of the case. The fingers 18 and 19 are then bent or formed at right angles to the top 31 and bottom 32 of the housing case 21, by any suitable assembly method, so that the fingers project toward each other through the notches 16 and 17, in the edges of pole pieces 11 and 12, and across open side 26.

The strike plate 23 is made of magnetic material, such as steel. A screw hole 38 is drilled through the strike plate, and sharp, protruding edges 39 are formed in the plate, as indicated in FIGURES 2 and 4, to retain the plate in fixed position on a door 22, for example, in alignment with a housed magnet assembly. The magnet assembly is mounted on the bottom of a shelf 59, while screw 41 is driven into the door to fasten the plate thereto. The exposed face of strike plate 23 is given a smooth finish to make maximum contact with the edge portions 13 and '14 of the pole pieces. These edge portions also are smoothly finished for the same reason.

Housing case 21 containing installed magnet 10 and pole pieces 11 and 12, as previously described, is mounted on the under side of shelf 59, for example, by means of screws 42 and 43 driven into the shelf through elongate screw holes 29 and 39 in cars 27 and 28, respectively. The elongate screw holes permit rapid and convenient positioning of case 21, adjacent the front edge of shelf 59, so that strike plate 23 is engaged by pole pieces 11 and 1-2 when door 22 is closed against door frame member 44.

The overall dimensions of the magnet 10 and the pole pieces 11 and 12 are made less than the inside dimensions of the housing case 21, and the ends of the magnet and of the pole pieces, as mentioned above, are made to converge several degrees inwardly from the inside surfaces of ends 33 and 34 of the case. Notches 16 and 17 in the pole pieces are made slightly wider thanfingers 18 and 19, as best shown in FIGURE 5. It will be observed that, in view of these dimensional and structural relationships, the magnet 10 and pole pieces 11 and 12 fit loosely inside the housing case 21. The magnet and pole pieces can readily slide as a unit on the smooth inside surface of case bottom 32. Sliding movement can take place side- Wise, end-wise or up and down inside case 21, without any danger of jamming therein. As pointed out above, this facilitates rapid adjustment of the position of the magnet and pole pieces with that of the strike plate for maximum magnetic attraction of the plate.

The fingers l8 and 19 limit the movement of the protruding edge portions 13 and 14 of the pole pieces out of case 21 through open side 26, when door 22 is closed against door jamb or frame member 44, but do not interfere with the side-wise, end-wise, or up and down floating movement of the pole pieces in adjusting their position relative to strike plate 23, for maximum attraction between the pole pieces 11 and 12 and the plate. Instead, the fingers 18 and '19 act as a fulcrum for pivot plate 29, and balance the magnet and pole pieces as a unit, to facilitate the above-described pivotal floating movement of the magnetic unit about a central axis passing through the transverse center line of fingers 18 and 19, and the pivot point of the pivotal convex surface of pivot plate 20. As a result of this adjustment action, pole pieces 11 and 12 engage the exposed surface of strike plate 23 uniformly and strongly throughout the full lengths and total surfaces of the protruding edges 13 and 14, as described above.

When door 22 is opened, the pull on the strike plate 23 pulls the pole pieces 11 and 1 2 against fingers 18 and 19 until the manual pulling force overcomes the force of magnetic attraction. Because of the floating pivotal movement of the magnetic unit, involving a balancing of the unit at the center line of the fingers 18 and 19, the opposed forces act uniformly over the surfaces of contact between pole pieces Y11 and 12 and strike plate 23, and at substantially right angles to those surfaces. As a result, the disengagement between the pole pieces and strike plate takes place suddenly and completely.

It will be observed that the specific embodiment described above provides a magnetic latch that holds a door closed tightly against rattling, and is constructed of relatively few parts that are capable of being mass-produced economically. The parts of the latch can be assembled rapidly and the assembled latch can be installed easily and conveniently.

The foregoing description is given primarily for explanatory purposes to illustrate a specific embodiment of my invention. It is understood that many variations in the structure, design and details of the invention will occur to one skilled in the art, and that the invention can be applied to various objects other than cabinets, cupboards and closets, and includes applications to the latching of windows as well as doors and other members. Accordingly, it is understood that such applications and such changes and modifications in the structure, design and details'of the specific embodiment of my invention, illustrated and described above, may'be made within the scope of the appended claims without departing from the spirit of the invention.

While I have herein shown and described my invention in what I have conceived to be the most practical and preferred embodiment, it is recognized that departures can be made therefrom within the scope of my invention, whichisnot'to be limited to the details disclosed herein but is to be accorded the full scope of the claims so as to embrace any and all equivalent structure.

Having described my invention, what I claim as new and desire to secure by Letters Patent is:

1. A magnetic latch comprising a magnet, pole pieces attracted to the magnet, mounted for independent movement relative to said magnet and to each other, and having exposed sliding surfaces, a housing of nonmagnetic material for slidably retaining therein the magnet and pole pieces attracted thereto with portions of the pole pieces projecting from the housing, the projecting portions of the pole pieces having notches formed therein, projections extending from the housing into the notches of the projecting portions of the pole pieces for retaining the pole pieces in vthe housing in loose relationship therewith, and pivot means associated with the projecting portions of the pole pieces and the projections extending from the housing for pivotal movement of the projecting portions of the pole pieces relative to the housing, said pivot means being mounted in the notches in the projecting portions of the pole pieces and being provided with a convex surface for hearing on the projections extending from the housing.

2. A magnetic latch comprising two generally fiat pole pieces, a generally flat magnet sandwiched between said 5 pole pieces and attracted to the magnet, a housing of nonmagnetic material containing the magnet and pole pieces loosely mounted therein for relative, limited independent movement in all directions with edges of the pole 5 pieces projecting from the housing, aligned notches formed midway in a pair of adjacent projecting edges of the pole pieces, aligned projections extending from the housing into the notches for retaining the pole pieces in the housing, and pivot means associated with the projecting edges of the pole pieces and the aligned projections of the housing for pivoting and retaining the pole pieces in the housing in balanced relationship against attractive forces of the magnet for an armature plate, said pivot means being mounted in the notches in the projecting portions of the pole pieces and being provided with a convex surface for hearing on said aligned projections of the housing.

References Cited in the file of this patent UNITED STATES PATENTS 2,240,035 Catherall Apr. 29, 1941 2,701,158 Schmitt Feb. 1, 1955 2,935,352 Heppner May 3, 1960 

